Firebase启动报错：FirebaseApp.options中projectId需为字符串

错误信息 #

node-express-firebase-main\node_modules\@firebase\component\dist\index.cjs.js:134
                throw e;
                ^

    Error [FirebaseError]: projectId must be a string in FirebaseApp.options
        at new FirestoreError (C:\Users\Vishnu Reddy\Desktop\FreshPrints\node-express-firebase-main\node_modules\@firebase\firestore\dist\index.node.cjs.js:153:28)
        at Function.Firestore.databaseIdFromApp (C:\Users\Vishnu Reddy\Desktop\FreshPrints\node-express-firebase-main\node_modules\@firebase\firestore\dist\index.node.cjs.js:22161:19)
        at new Firestore (C:\Users\Vishnu Reddy\Desktop\FreshPrints\node-express-firebase-main\node_modules\@firebase\firestore\dist\index.node.cjs.js:22035:42)
        at C:\Users\Vishnu Reddy\Desktop\FreshPrints\node-express-firebase-main\node_modules\@firebase\firestore\dist\index.node.cjs.js:23398:16
        at Component.instanceFactory (C:\Users\Vishnu Reddy\Desktop\FreshPrints\node-express-firebase-main\node_modules\@firebase\firestore\dist\index.node.cjs.js:23373:16)
        at Provider.getOrInitializeService (C:\Users\Vishnu Reddy\Desktop\FreshPrints\node-express-firebase-main\node_modules\@firebase\component\dist\index.cjs.js:222:39)
        at Provider.getImmediate (C:\Users\Vishnu Reddy\Desktop\FreshPrints\node-express-firebase-main\node_modules\@firebase\component\dist\index.cjs.js:120:33)
        at FirebaseAppImpl._getService (C:\Users\Vishnu Reddy\Desktop\FreshPrints\node-express-firebase-main\node_modules\@firebase\app\dist\index.node.cjs.js:230:49)
        at FirebaseAppImpl.firebaseAppImpl.<computed> [as firestore] (C:\Users\Vishnu Reddy\Desktop\FreshPrints\node-express-firebase-main\node_modules\@firebase\app\dist\index.node.cjs.js:442:39)
        at Object.<anonymous> (C:\Users\Vishnu Reddy\Desktop\FreshPrints\node-express-firebase-main\controllers\ApparelController.js:5:28) {
      code: 'invalid-argument',
      toString: [Function (anonymous)]
    }

问题根源 #

你的.env文件存在两个致命问题：

1. 格式错误：.env是环境变量配置文件，只能用KEY=VALUE的键值对格式，不能使用JavaScript的export default模块语法，Firebase无法识别这种格式的配置。
2. 语法错误：authDomain和messagingSenderId的引号未正确闭合，导致配置值读取异常。

修正后的.env文件 #

NODE_ENV=production
#express server config
PORT=8080
HOST=localhost
HOST_URL=http://localhost:8080

#firebase database config
FIREBASE_API_KEY=<API_KEY>
FIREBASE_AUTH_DOMAIN=<AUTH_DOMAIN>
FIREBASE_PROJECT_ID=<PROJECT_ID>
FIREBASE_STORAGE_BUCKET=<STORAGE_bucket>
FIREBASE_MESSAGING_SENDER_ID=<message_sender_id>
FIREBASE_APP_ID=<APP_ID>

代码中读取配置的正确方式 #

确保你已经安装了dotenv包（npm install dotenv），然后在项目入口文件中加载环境变量，再初始化Firebase：

require('dotenv').config();

const firebase = require('firebase/app');
require('firebase/firestore');

const firebaseConfig = {
  apiKey: process.env.FIREBASE_API_KEY,
  authDomain: process.env.FIREBASE_AUTH_DOMAIN,
  projectId: process.env.FIREBASE_PROJECT_ID,
  storageBucket: process.env.FIREBASE_STORAGE_BUCKET,
  messagingSenderId: process.env.FIREBASE_MESSAGING_SENDER_ID,
  appId: process.env.FIREBASE_APP_ID
};

firebase.initializeApp(firebaseConfig);
const db = firebase.firestore();

内容的提问来源于stack exchange，提问作者mavilla vishnu vardhan